1. Field of the Invention
The present invention relates in general to an illuminated touch sensitive switch, and more specifically, to an electroluminiescent touch switch.
2. Description of the Related Art
Vehicle accessory input controls typically consist of devices which require rotating a control knob, depressing a control button, or sliding a mechanical or electro-mechanical control switch to operate or adjust a vehicle accessory device such as a radio, CD player, or climate control. An exterior casing or oversize buttons and knobs are typically used to dress up and conceal the gaps between the bezel and the movable components of the input control devices. Despite the addition of these facial coverings to make the appearance presentable and visually appealing, the plurality of interlocking components leaves way for dirt and debris to lodge in the gaps and crevices between these interlocking components. Devices such as appliances have been known to use switches under the surface of a fascia of the appliance to create a sealed environment, however, these devices have been limited to a physical press and release operation.
Capacitive sensors are sometimes used as a switch actuator. A capacitive sensor disposed under a surface fascia creates a capacitance above the fascia surface which varies in the presence of conductive objects placed nearby. A change of capacitance is sensed in order to initiate a request by an operator to actuate a switch.
In order to use capacitive switches in dark environments (e.g. a car at night), dedicated lighting with a device may be necessary. LEDs may be used in conjunction with a capacitive switch (e.g., backlighting). However, either a large number of LEDs must be used, or the LEDs must be positioned to illuminate more than one button or incorporate light piping to tunnel the light to a plurality of switches. An individual LED used to illuminate more than one switch often produces uneven distribution of lighting on each switch.
Electroluminescence (EL) lighting uses a phosphor layer within an EL film that is excited by a high voltage source to produce an even distribution of lighting. An EL film has been formed on the top surface of a capacitive switch for illuminating the switch. However, prior systems have used the same high voltage A/C signal to excite the phosphor layer and to generate the electric field used to detect switch actuation. Using a high voltage A/C source to generate the electric field may result in a driver or passenger receiving a high voltage shock. Furthermore, prior capacitive switches integrated with EL lighting have required an excessive number layers. Additional layering adds thickness and cost to the switch.